How to Propagate hydrangea 'Nikko Blue'?
Propagate by softwood cuttings in early summer, or by hardwood cuttings in winter

hydrangea 'Nikko Blue' · Hydrangea macrophylla 'Nikko Blue'
Grow in moist but well-drained, humus rich soil, in a lightly shaded spot with shelter from cold, drying winds. Mulch annually in spring. Soil additives may be required to maintain specific flower colours; blue colours are best maintained by growing in acidic soil or ericaceous compost. See shrubby hydrangea cultivation for more detailed advice
Propagate by softwood cuttings in early summer, or by hardwood cuttings in winter